[sdiy] VCF schematic

[Charles Bisaillon]

Hi,

The capstone VCF is a simultaneous LP/BP/HP with FM capabilities, variable
input gain and input clip LED indicator. The design is alright, it has some
quarks but they might come in handy at times. The Band Pass is the output
that is the less reliable, it has lower signal than the other outputs when
the resonance is off, but it's full of tricks with resonance full (I got it
to imitate a Harley Davidson rhythmic pattern with a constant 50Hz square
wave).

I've also had a lot of troubles with the resonance circuit, it doesn't feel
like it is a linear pot I'm turning, the resonance creeps in exponentially
as I twist the knob. Choosing the right resistors was a big compromise game.
I've tried many things but I reach my limit of understanding.

There was also a lot of phase cancellation issues but I got most of that
fixed, the only quark left from that can be heard in the high pass filter
with high resonance, the volume suddenly drops a couple of dBs at a certain
cutoff frequency.

Anyways, I'm not too worried about this and other small things, the
schematic is accepted, the VCF is considered finished.

http://www.oveloe.com/490/vcf_sch.jpg

Cheers

Charles